High-frequency electrical apparatus



0d. 10, 1944. v R N ETAL 2,359,811

HIGH FREQUENCY ELECTRICAL APPARATUS Original Filed March 1, 1938' "lawman-w" INVENTOR. RUSSELL H. VARIAN WILLIAM w. HANSEN- THEIR ATTORNEY Patented Oct. 10, 19

2,359,811 men-mommy nmo'rmcsr.

APPARATUS Russell H. Varian, Bellmore, and William W. Hansen, Garden City, N. Y., assignors to The Board of Trustees of the Leland Stanford Junior University, Stanford University, Calif., a corporation of California Original application March 1, 1938, Serial No.

193,268, now Patent No. 2,272,165, dated February 3. 1942. Divided and this application January 29. 1942, Serial No. 428.691

Claims.

The present invention relates, generally, to the controlof electron beams by electromagnetic fields for the excitation of electric circuits, and

A has reference, in particular, to novel electrical high frequency apparatus in which electron beams are subjected to displacement by electromagnetic fields confined and maintained in hollow conductors.

The present invention is, a division of co-pending application, Serial No. 193,268, filed March 1, 1938, for High frequency electrical apparatus, Patent No. 2,272,165 issued February 3, 1942. The embodiment of the present invention utilizes some of the elements of Patent No. 2,190,712, February 20, 1940, William W. Hansen.

This invention has for its principal object the provision of a novel high frequency electrical apparatus adapted for the excitation of electric circuits by periodically transversely displacing an electron beam, the displacement of which requires less power than that rendered available as high frequency energy as the result of the deflection of the beam, whereby the energy of an electron all the principal functional operations ordinarily associated with the generation, amplification, modulation, and transmission of high frequency oscillations.

Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawing wherein the single figure is an embodiment in which an electron beam is initially given lateral displacement by a hollow resonator, and electric fields are then used to change the velocities of the electrons of the beam thereby converting transverse movement of the beam to density modulation of the electrons and then absorbing energy from the beam by use of a second hollow resonator.

In the drawing an electron source I emits a beam of electrons 2 that is accelerated toward the wall of a resonator 3 and into which it passes through a grid Ill in the resonator wall. A confined system of standing waves is produced between faces 4 and 4' of resonator 3. The resonator beam passes between the faces 4 and 4'. whereby an oscillating electric field is impressed upon the electron beam acting to deflect the electron beam first toward the face 4 and then toward the other face 4'. The beam traverses member 3 and exits through grid opening 5 where it enters an electrostatic field between grid 5 and an oblique grid 5 maintained by the battery shown. A second electrostatic field is maintained between another oblique grid I and a transverse grid 8. After leaving the field through grid 8 the electrons enter an alternating field between spaced grids I IV of a second resonator 9. The two resonators 3 and 3 are shown coupled together by coupling loops l2 and I3 in the manner indicated.

In operation, the electron beam is periodically shifted from side to side so that it moves in the way represented from right to left and reverse in the figure as it passes downward through grids 5 to 8. Grids 5 and 8 are both preferably positive with reference to the electron emitter. Grids 5 and I are both at a potential materially different from that of grids 5 and 8, preferably only slightly positive in reference to the electron emitter.

An electron entering the field between grids 5 and 8 is either accelerated or decelerated depending upon the relative polarity of grids 5 and 3. For convenience it will be assumed that grids 6 and I are negative in respect to grids 5 and 8. Then an electron will be decelerated in the space between grids 5 and 6. Its velocity will be unaffected between grids 6 and l and it will be accelerated between grids l and 8. The resultant change in velocity between grid 5 and grid 8 will be zero. However, thetime taken by an electron in transit from grid 5 to grid 8 will vary depending upon its transverse position in the fields the electron traverses. If it is toward the left side of the beam as represented in the drawing, and

grids 5 and I are negative with respect to grids 5' and 8, the electron is very'quickly decelerated and it travels at the reduced velocity the comparatively long distance from grid 6 to grid 1. Between grids I and 8 it is quickly accelerated to its original speed. If it is located toward the right side of the beam the electron will be more gradually decelerated in the space between grids 5 and 6. It will travel a. relatively short distance between grids 6 and I at the reduced speed and it will be relatively slowly accelerated to its original speed between grids l and 8. Thus, it will take less time for the electron to go from grid 5 to grid 8 in a region where grids G and I are close together than where they are farther apart. The

reverse is true if the outer grids are made negative and the inner ones positive. When the electron beam is oscillating laterally some electrons will get from the emitter to the region beyond grid 8 in less time than others. The result is that the transit time from grid to grid 8 is a function of beam deflection, and it is possible for electrons leaving grid 5, after some other electrons, to have a shorter travel time between the emitter I and grid 8 and to arrive at grid 8 at the same time as those that left the emitter earlier, thus forming a periodic electron concentration. This has the efiect of making the electron stream where it leaves grid 8 periodically non-uniform, that is, recurrently grouped or bunched. The electron beam travels on and enters the field between the spaced grids H of a hollow resonator 9 which is caused to oscillate by the bunched electron beam as explained by Patent No. 2,190,712. In the terminology used herein in apparatus of this kind, the means included between the emitter i and grid 8 is called a buncher. Its function is briefly set forth as that of converting a substantially uniform-electron beam, or one varying at low frequency, into one that varies in density, that is, grouped, at high frequency. The oscillating resonator 9 delivers energy to the buncher through the interconnected coupling loops l2 and I3.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In apparatus of the kind described, means for producing a beam of electrons, means for effecting oscillating transverse displacement of said beam at a high frequency, a hollow resonator having a confined system of standing waves for receiving said electron beam, said apparatus embodying means for varying the transit time of the electrons of said beam in their passage to said system of standing waves in accordance with the transverse displacement of said electrons to thereby produce recurrent grouping of the electrons of said beam as they enter said hollow resonator due to said variable transit time.

2. In apparatus of the kind described, the

' combination of means for producing an electron beam, means for deflecting said beam transversely, and means for causin the time of flight of the electrons of said electron beam between their source and a plane perpendicular to the initial path of the beam surface to vary as a function of the transverse displacement of said beam and at the frequency of said transverse displacement.

3. In apparatus of the kind described, the combination of means for producing an electron beam, means for oscillating said beam transversely, a resonant circuit excited by said beam, and means interposed between said oscillating means and said circuit for varying the transit time of said electrons as a function of the transverse displacement of the beam from its central position.

4. Apparatus of the character described, the combination of emitter means, a. hollow resonator disposed in advance of said emitter means, means for driving a stream of electrons from said emitter means and through said hollow resonator, the field of said resonator acting to oscillate said stream transversely, a second hollow resonator spaced from said first hollow resonator, coupling means between said two hollow resonators, and a pair of obliquely inclined grids interposed between said hollow resonators and connected to said driving means for varying the transit time of electrons passing between said resonators in accordance with the transverse displacement of said electrons.

5. High frequency apparatus comprising means for producing an electron stream, means for oscillating said stream transversely, a resonant circuit spaced from said oscillating means and excited by said stream, and means interposed between said oscillating means and said circuit 'for causing recurrent grouping of the electrons of said stream in accordance with the transverse displacement of said stream as they excite said resonant circuit.

RUSSELL H. VARIAN.

WILLIAM W. HANSEN. 

